Add name field to ExportOutput

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: davidwzhao

meta/src/meta/grammar.y

@@ -1339,10 +1339,11 @@ export
 # Like `export`, but the engine treats the result as part of the transaction results
 # and chooses the output path itself (so no `path` is specified here).
 export_output
-    : "(" "export_output" export_csv_output ")"
-      construct: $$ = transactions.ExportOutput(csv=$3)
+    : "(" "export_output" name export_csv_output ")"
+      construct: $$ = transactions.ExportOutput(name=$3, csv=$4)
       deconstruct if builtin.has_proto_field($$, 'csv'):
-        $3: transactions.ExportCSVOutput = $$.csv
+        $3: String = $$.name
+        $4: transactions.ExportCSVOutput = $$.csv
 
 export_csv_output
     : "(" "csv" export_csv_source csv_config ")"

proto/relationalai/lqp/v1/transactions.proto

@@ -182,9 +182,11 @@ message ExportCSVOutput {
 }
 
 message ExportOutput {
+  string name = 1;
+
   // Supports export formats e.g., CSV and Iceberg, but considered to be part of txn results
   oneof export_output {
-    ExportCSVOutput csv = 1;
+    ExportCSVOutput csv = 2;
   }
 }